Base station device and wireless communication method

ABSTRACT

A direction of arrival estimation section  106  estimates the direction of arrival of a signal, and a DSCH-using terminal determination section  108  determines a communication terminal that is to use a DSCH based on communication terminals from which a request signal is received and signal direction of arrival. That is to say, the DSCH-using terminal determination section  108  determines communication terminals that are to use the DSCH in the order of communication terminals whose signal directions of arrival are most contiguous from among communication terminals wishing to use the DSCH.

TECHNICAL FIELD

[0001] The present invention relates to a base station apparatus andradio communication method for use in high-speed data communication.

BACKGROUND ART

[0002] One multiple access method in a digital radio communicationsystem is CDMA (Code Division Multiple Access). In a standardestablished by 3GPP (3rd Generation Partnership Project), a standardsbody related to mobile radio communication systems, this CDMA method isused and a Downlink Shared Channel (DSCH) used for high-speed datacommunication in a downlink (a channel from a base station to acommunication terminal) is stipulated as one channel shared by aplurality of communication terminals (hereinafter referred to as “sharedchannel”).

[0003] As this DSCH is used by being assigned to each communicationterminal on a specified transmission unit basis (for example, on aframe-by-frame basis), its use is anticipated in down link high-speedpacket transmission, etc.

[0004] In a CDMA system, there are cases where an adaptive array(hereinafter abbreviated to “AAA”) is used with the object of reducinginterference. This adaptive array is a technology whereby a base stationis equipped with an array antenna comprising a plurality of antennaelements, and directivity is formed by multiplying a transmit signal bya complex coefficient (hereinafter this complex coefficient is referredto as a “weight”), and performing transmission in line with thatdirectivity.

[0005] However, since the above-described DSCH is assigned tocommunication terminals on a per-predetermined-transmission-unit basis,when an adaptive array is applied to DSCH signal transmission, and DSCHsignal transmission is performed with a different directivity formed foreach communication terminal, directivity is switched every DSCH signaltransmission unit. Also, as the DSCH is a channel used for high-speedcommunication, the DSCH signal power is extremely high compared with adedicated channel signal.

[0006] Thus, when the DSCH is assigned to a particular communicationterminal, interference imposed on a dedicated channel signal from theDSCH signal suddenly increases in communication terminals located in thevicinity of a communication terminal to which the DSCH is assigned, andtherefore, as shown in FIG. 1, the increase in dedicated channel signaltransmission power due to transmission power control in a downlink (achannel from abase station to a communication terminal) (transmissionpower control that increases or decreases transmission power at a basestation according to a transmission power increase/decrease command froma communication terminal) cannot keep up with the increase ininterference power conveyed from the DSCH signal. There is thus aproblem of the occurrence of major deterioration of dedicated channelsignal reception quality (for example, the reception SIR) incommunication terminals located in the vicinity of a communicationterminal to which the DSCH is assigned, and obstruction ofcommunication. Moreover, since interference power fluctuates abruptly,there is a problem of loss of CDMA system stability and a decrease insystem capacity.

DISCLOSURE OF INVENTION

[0007] It is an object of the present invention to provide a basestation apparatus and radio communication method that make it possibleto prevent a major deterioration of dedicated channel signal receptionquality even when an adaptive array is used for shared channel signaltransmission.

[0008] The present inventors arrived at the present invention by notingthat a cause of major deterioration of dedicated channel signalreception quality lies in the fact that, when an adaptive array isapplied to shared channel signal transmission, the difference betweenthe transmission power value of the dedicated channel signal and thetransmission power value of the shared channel signal suddenly becomeslarge in a communication terminal located in the vicinity of acommunication terminal to which the shared channel is assigned, andfinding that it is possible to support normal transmission power controlin a dedicated channel signal downlink by reducing this difference intransmission power values.

[0009] Thus, in order to achieve the above object, the present inventionalleviates the effect of interference imposed on a dedicated channelsignal by a shared channel signal by reducing the difference between thetransmission power value of a shared channel signal for a communicationterminal to which a shared channel is assigned and the transmissionpower value of a dedicated channel signal for a communication terminallocated in the vicinity of that communication terminal to which theshared channel is assigned.

[0010] That is to say, the present invention reduces the differencebetween the transmission power value of a dedicated channel signal andthe transmission power value of a shared channel signal by graduallyincreasing interference imposed on a communication terminal located inthe vicinity of a communication terminal to which the shared channel isassigned prior to shared channel signal transmission.

[0011] Also, the present invention reduces the difference between thetransmission power value of a dedicated channel signal and thetransmission power value of a shared channel signal beforehand byincreasing the transmission power value of a dedicated channel signalfor a communication terminal located in the vicinity of a communicationterminal to which the shared channel is assigned in correspondence tothe amount of increase of the shared channel signal transmission powervalue. 5 Furthermore, the present invention provides sufficient time forreducing the difference between the dedicated channel signaltransmission power value and shared channel signal transmission powervalue by means of normal transmission power control on a dedicatedchannel signal downlink by extending the time during which the amount ofinterference imposed by the shared channel signal on a communicationterminal located in the vicinity of a communication terminal to whichthe shared channel is assigned is held constant.

BRIEF DESCRIPTION OF DRAWINGS

[0012]FIG. 1 is a drawing showing changes in interference power in acommunication terminal when DSCH assignment is performed by aconventional base station apparatus;

[0013]FIG. 2 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 1 of the presentinvention;

[0014]FIG. 3 is a drawing showing radiation patterns for explaining theoperation of a base station apparatus according to Embodiment 1 of thepresent invention;

[0015]FIG. 4 is a drawing showing changes in interference power in acommunication terminal when DSCH assignment is performed by a basestation apparatus according to Embodiment 1 of the present invention;

[0016]FIG. 5 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 2 of the presentinvention;

[0017]FIG. 6 is a drawing showing radiation patterns for explaining theoperation of a base station apparatus according to Embodiment 2 of thepresent invention;

[0018]FIG. 7A is a table for explaining the DSCH assignment order methodof a base station apparatus according to Embodiment 2 of the presentinvention;

[0019]FIG. 7B is a table for explaining the DSCH assignment order methodof a base station apparatus according to Embodiment 2 of the presentinvention;

[0020]FIG. 8 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 3 of the presentinvention;

[0021]FIG. 9 is a drawing showing changes in interference power in acommunication terminal when DSCH assignment is performed by a basestation apparatus according to Embodiment 3 of the present invention;

[0022]FIG. 10 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 4 of the presentinvention;

[0023]FIG. 11A is a drawing showing time-wise changes in dedicatedchannel signal transmission power and DSCH signal transmission power ina base station apparatus according to Embodiment 4 of the presentinvention;

[0024]FIG. 11B is a drawing showing time-wise changes in dedicatedchannel signal transmission power and DSCH signal transmission power ina base station apparatus according to Embodiment 4 of the presentinvention;

[0025]FIG. 12 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 5 of the presentinvention;

[0026]FIG. 13 is a main block diagram showing a schematic configurationof a communication terminal apparatus according to Embodiment 5 of thepresent invention;

[0027]FIG. 14 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 6 of the presentinvention; and

[0028]FIG. 15 is a drawing showing radiation patterns for explainingtransmission directivity control performed by a base station apparatusaccording to Embodiment 6 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0029] With reference now to the accompanying drawings, embodiments ofthe present invention will be explained in detail below.

[0030] In the following descriptions, a case is described where a DSCHis used as a shared channel, but this is not a limitation, and thefollowing embodiments can also be implemented in a case where a channelother than a DSCH is used as a shared channel.

[0031] (Embodiment 1)

[0032] In this embodiment, a case is described where an adaptive arrayis applied to DSCH signal transmission, and the DSCH is assigned tocommunication terminals in an order such that the difference in signaldirection of arrival is minimized in the communication terminal to whichthe DSCH is assigned this time and the communication terminal to whichthe DSCH will be assigned next time.

[0033]FIG. 2 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 1 of the presentinvention.

[0034] Signals on uplinks (channels from communication terminals to abase station) received via antennas 101 through 104 are received via atransmission/reception separator 105, and after undergoing predeterminedradio reception processing (down-conversion, A/D conversion, etc.), aresent to a direction of arrival estimation section 106. In the directionof arrival estimation section 106, the received signals undergo arraycombining processing, after which despreading processing is performedand the received signal of each communication terminal (user) isextracted, and a direction of arrival is estimated for the receivedsignals from the respective communication terminals. The results of thisdirection of arrival estimation are sent to an AAA directivitycontroller 111 and a DSCH-using terminal determination section 108. Inaddition, the received signals undergo demodulation processing by ademodulator 107 for each communication terminal and become receiveddata.

[0035] A direction of arrival estimation section 106 and demodulator 107are provided for each communication terminal (MS), and received data foreach communication terminal (MS#1 received data through MS#n receiveddata) is obtained from the respective demodulators 107.

[0036] Received data that has undergone demodulation processing is sentto the DSCH-using terminal determination section 108. In the DSCH-usingterminal determination section 108, the communication terminal that willuse the DSCH is determined based on communication terminals that havetransmitted a request signal indicating a wish to use the DSCH and thedirection of arrival of the signals transmitted from the respectivecommunication terminals (that is, the directions estimated by thedirection of arrival estimation section 106). The determination methodwill be described later herein. The DSCH-using terminal determinationsection 108 sends this determined information to a data selector 109.

[0037] The data selector 109 selects the DSCH data of the communicationterminal that will use the DSCH from the DSCH data of each communicationterminal (MS#1 DSCH data through MS#n DSCH data), and sends this to adata modulator 110. The data modulator 110 performs modulationprocessing and spreading processing on the DSCH data, and then sends aspread DSCH signal to the AAA directivity controller 111.

[0038] A data modulator 110 and AAA directivity controller 111 areprovided for each communication terminal (MS).

[0039] The AAA directivity controller 111 forms a transmissiondirectivity based on direction of arrival information estimated by thedirection of arrival estimation section 106. That is to say, the AAAdirectivity controller 111 multiplies the DSCH signal from the datamodulator 110 by weights corresponding to transmission directionalities(weights corresponding to antennas 101 through 104). DSCH signalsmultiplied by the weights are transmitted to the communication terminalsfrom antennas 101 through 104 via the transmission/reception separator105.

[0040] Next, the operation of a base station apparatus that has theabove configuration will be described.

[0041] When a communication terminal requests use of the DSCH, ittransmits a request signal to the base station on an uplink channel. Inthe base station, the request signal is demodulated by the demodulator107, and then sent to the DSCH-using terminal determination section 108.The results of received signal direction of arrival estimation by thedirection of arrival estimation section 106 are sent to the DSCH-usingterminal determination section 108. The results of received signaldirection of arrival estimation by the direction of arrival estimationsection 106 are also sent to the DSCH-using terminal determinationsection 108. In the DSCH-using terminal determination section 108, thecommunication terminal that will use the DSCH is determined from thecommunication terminals from which a request signal was received and thedirection of arrival of the received signals.

[0042] That is to say, all request signals are input to the DSCH-usingterminal determination section 108, and it is therefore possible for theDSCH-using terminal determination section 108 to identify communicationterminals that wish to use the DSCH. Also, since all direction ofarrival estimation results for signals transmitted from communicationterminals are input to the DSCH-using terminal determination section108, it is possible for the DSCH-using terminal determination section108 to determine communication terminals that will use the DSCH in orderfromthe communication terminal whose direction of arrival is closestamong communication terminals that wish to use the DSCH. That is to say,in the DSCH-using terminal determination section 108, the DSCH issuccessively assigned to communication terminals in order so that thedifference in signal direction of arrival is minimized between thecommunication terminal to which the DSCH is assigned this time and thecommunication terminal to which the DSCH will be assigned next time. Theassignment method will be described in detail later herein.

[0043] When a communication terminal that will use the DSCH isdetermined by the DSCH-using terminal determination section 108, thatinformation is sent to the data selector 109. As DSCH data for allcommunication terminals (MS#1 DSCH data through MS#n DSCH data) is inputto the data selector 109, the data selector 109 selects only DSCH dataof the communication terminal that will use the DSCH from the DSCH datainput to the data selector 109, and outputs this to the data modulator110. In the data modulator 110, modulation processing is executed on theDSCH data for the communication terminal that will use the DSCH. In thedata modulator 110, also, spreading processing is performed, using apredetermined spreading code, on DSCH data that has undergone modulationprocessing. DSCH data that has undergone spreading processing is sent tothe AAA directivity controller 111.

[0044] In the AAA directivity controller 111, DSCH signal directivity iscontrolled based on directions of arrival estimated from receivedsignals from communication terminals. That is to say, the AAAdirectivity controller 111 calculates a weight that will direct a beamto a communication terminal that transmits a signal on the DSCH, andmultiplies the DSCH signal by that weight. A DSCH signal multiplied by aweight is transmitted to a communication terminal for which directivityhas been directed-that is, the communication terminal that will use theDSCH.

[0045] Next, the DSCH assignment method will be described in detail.FIG. 3 is a drawing showing radiation patterns for explaining theoperation of a base station apparatus according to Embodiment 1 of thepresent invention, and FIG. 4 is a drawing showing changes ininterference power in a communication terminal when DSCH assignment isperformed by a base station apparatus according to Embodiment 1 of thepresent invention.

[0046] In FIG. 3, request signals indicating a wish to use the DSCH aretransmitted to a base station (BS) according to this embodiment from,for example, communication terminals (MS) #1, #2, and #3. Also, sinceall direction of arrival estimation results for signals transmitted fromcommunication terminals are input to the DSCH-using terminaldetermination section 108, the DSCH-using terminal determination section108 successively assigns the DSCH to communication terminals #1 through#3 in order starting from the smallest angle indicating the direction ofarrival.

[0047] That is to say, the DSCH-using terminal determination section 108first assigns the DSCH to communication terminal #1, which has thesmallest angle indicating direction of arrival within nondirectionaltransmission area 201, then assigns the DSCH to communication terminal#2, which has the smallest difference in direction of arrival fromcommunication terminal #1, and then assigns the DSCH to communicationterminal #3, which has the smallest difference in direction of arrivalfrom communication terminal #2. Reference code 202 indicates theradiation pattern when a DSCH signal is transmitted to communicationterminal #1, reference code 203 indicates the radiation pattern when aDSCH signal is transmitted to communication terminal #2, and referencecode 204 indicates the radiation pattern when a DSCH signal istransmitted to communication terminal #3.

[0048] Here, to consider communication terminal #5 located in thevicinity of communication terminal #2, when DSCH assignment is performedas described above, interference received from the DSCH signal by adedicated channel signal transmitted to communication terminal #5gradually changes as shown in FIG. 4.

[0049] That is to say, as the DSCH is assigned in the ordercommunication terminal #1 communication terminal #2 communicationterminal #3, in communication terminal #5 located in the vicinity ofcommunication terminal #2, interference power received from the DSCHsignal gradually increases as the transmission directivity of the DSCHsignal approaches that terminal, and interference power received fromthe DSCH signal gradually decreases as the transmission directivity ofthe DSCH signal moves way from that terminal.

[0050] To be specific, as shown in FIG. 4, first, at t1, the DSCH isassigned to communication terminal #1, and therefore interference powerin communication terminal #5 increases from P0 to P1, and remains at P1until t2 when the DSCH is assigned to communication terminal #2. Then,at t2, since the DSCH is assigned to communication terminal #2,interference power in communication terminal #5 increases from P1 to P2,and remains at P2 until t3 when the DSCH is assigned to communicationterminal #3. Then, at t3, since the DSCH is assigned to communicationterminal #3, interference power in communication terminal #5 decreasesfrom P2 to P3, and remains at P3 until t4 when DSCH assignment tocommunication terminal #3 ceases. Then, at t4, when DSCH assignment hasceased for all of communication terminals #1 through #3, interferencepower in communication terminal #5 decreases from P3 to P0.

[0051] In FIG. 4, P0 indicates interference power received by adedicated channel signal for communication terminal #5 from signalsother than a DSCH signal-that is, interference power received fromdedicated channel signals for other communication terminals within thesame cell, and the like.

[0052] Thus, for communication terminal #5 located in the vicinity ofcommunication terminal #2, since DSCH signal transmission directivitygradually approaches that terminal, interference power received from aDSCH signal also gradually increases. Therefore, as shown in FIG. 4, thetracking ability of transmission power control with respect to adedicated channel signal transmitted to communication terminal #5 isimproved. That is to say, increases in transmission power of a dedicatedchannel by means of transmission power control in a downlink can trackincreases in interference power from a DSCH signal. Thus, incommunication terminal #5, it is possible for deterioration of receptionquality due to interference received from a DSCH signal to be reduced bymeans of transmission power control.

[0053] In the above description, it has been assumed that the DSCH isassigned in order starting from communication terminal #1, which has thesmallest angle indicating direction of arrival, but the DSCH may also beassigned in order starting from communication terminal #3, which has thelargest angle indicating direction of arrival. That is to say, the DSCHmay be assigned in the order communication terminal #3→communicationterminal #2 communication terminal #1.

[0054] Thus, according to this embodiment, an adaptive array is appliedto DSCH signal transmission, and the DSCH is assigned to communicationterminals in order so that the difference in signal direction of arrivalis minimized between the communication terminal to which the DSCH isassigned this time and the communication terminal to which the DSCH willbe assigned next time, so that interference power received from a DSCHsignal increases gradually, and not abruptly, in a communicationterminal located in the vicinity of a communication terminal to whichthe DSCH is assigned, and therefore increases in dedicated channelsignal transmission power can track increases in interference powerreceived from the DSCH signal, and deterioration of reception qualitydue to interference received from the DSCH signal can be reduced.Furthermore, since interference power received from the DSCH signaldecreases gradually, the tracking ability of transmission power controlthat decreases dedicated channel signal transmission power is alsoimproved, making possible an increase in system capacity.

[0055] (Embodiment 2)

[0056] When the DSCH assignment order is determined in accordance withonly signal direction of arrival, as described in Embodiment 1 above,the assignment order is not necessarily the optimal assignment order forcommunication terminals requesting DSCH assignment. This is becausethere already exists a DSCH assignment priority order that takes accountof propagation path conditions, communication throughput, and so forth,indicated by the reception SIR, etc., for each communication terminalrequesting DSCH assignment.

[0057] Thus, in this embodiment, a case is described where the DSCHassignment order is determined in accordance with signal direction ofarrival, while taking account of this priority order. By this means itis possible to reduce deterioration of reception quality due tointerference received from a DSCH signal while performing optimalassignment from the viewpoint of DSCH signal transmission efficiency.

[0058]FIG. 5 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 2 of the presentinvention. Parts in FIG. 2 identical to those in Embodiment 1 areassigned the same codes as in Embodiment 1 and their detailedexplanations are omitted.

[0059] In FIG. 5, a demodulator 401 separates information (such as acommunication terminal reception SIR, for example) indicating downlinkchannel quality sent from a communication terminal from a demodulatedreceived signal, and sends this information to a DSCH-using terminaldetermination section 402. In the DSCH-using terminal determinationsection 402, the communication terminal that will use the DSCH isdetermined based on communication terminals that have transmitted arequest signal indicating a wish to use the DSCH, information indicatingdownlink channel quality, and the direction of arrival of the signalstransmitted from the respective communication terminals. That is to say,the DSCH-using terminal determination section 402 determines the DSCHassignment order by adding a priority order indicated by downlinkchannel quality to signal direction of arrival. To be specific, thisdetermination is carried out as described below.

[0060]FIG. 6 is a drawing showing radiation patterns for explaining theoperation of a base station apparatus according to Embodiment 2 of thepresent invention, and FIG. 7 shows tables for explaining the DSCHassignment order method of a base station apparatus according toEmbodiment 2 of the present invention.

[0061] In FIG. 6, it is assumed that request signals indicating a wishto use the DSCH are transmitted from communication terminals #1 through#6. Reference code 201 indicates the nondirectional transmission area,and reference codes 501 through 506 indicate the radiation patterns whenDSCH signals are transmitted to communication terminals #1 through #6,respectively.

[0062] The DSCH-using terminal determination section 402 first assigns apriority to each of communication terminals #1 through #6 according todownlink channel quality, and then adds the direction of arrival of thesignal transmitted from each of communication terminals #1 through #6 asan angle of arrival. Here, it is assumed that the received signal angleof arrival increases in the order of communication terminals #1 through#6 shown in FIG. 6. Also, it is assumed that downlink channel qualityimproves in the order: communication terminal #4, #2, #1, #3, #5, #6.Thus, the DSCH-using terminal determination section 402 first creates atable such as that shown in FIG. 7A.

[0063] Next, the DSCH-using terminal determination section 402calculates evaluation numeric values incorporating angle of arrival andpriority. That is to say, the DSCH-using terminal determination section402 calculates evaluation numeric values that take account of thedirection of arrival of each signal together with channel quality. Theevaluation numeric value is calculated using the following equation.

Evaluation numeric value=angle of arrival/(total number of communicationterminals transmitting a request signal+1−priority)

[0064] The divisors and evaluation numeric values are thus as shown inFIG. 7B.

[0065] The DSCH-using terminal determination section 402 then determinesthe DSCH assignment order in accordance with these evaluation numericvalues. That is to say, the DSCH-using terminal determination section402 assigns the DSCH in order starting from the communication terminalwith the lowest evaluation numeric value. Thus, in the example shown inFIG. 7B, the DSCH is assigned in the order: communication terminal #3,#2, #1, #4, #5, #6.

[0066] In this embodiment, evaluation numeric values are not limited toevaluation numeric values calculated using the above equation, and anyvalues may be used as long as they are evaluation numeric values thatenable the DSCH assignment order to be determined by taking account ofsignal direction of arrival together with channel quality.

[0067] Also, the angle used as the criterion for received signaldirection of arrival may be fixed anywhere within the range within whichcommunication terminals are present-that is, within the nondirectionaltransmission area.

[0068] Thus, according to this embodiment, the DSCH assignment order isdetermined using a value obtained by weighting a priority establishedaccording to downlink channel quality with a value indicating thedirection of arrival of a signal, thereby making it possible to performoptimal DSCH assignment that takes both downlink channel quality andsignal direction of arrival into consideration. It is thus possible toreduce deterioration of reception quality due to interference receivedfrom a DSCH signal while performing optimal assignment from theviewpoint of DSCH signal transmission efficiency.

[0069] (Embodiment 3)

[0070] In this embodiment, a case is described where, prior to the startof DSCH signal transmission, a dummy signal is transmitted whilegradually increasing its transmission power. By this means, acommunication terminal located in the vicinity of a communicationterminal to which the DSCH is assigned receives interference from a DSCHsignal after interference power has been gradually increased.

[0071]FIG. 8 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 3 of the presentinvention. Parts in FIG. 8 identical to those in Embodiment 1 areassigned the same codes as in Embodiment 1 and their detailedexplanations are omitted.

[0072] In FIG. 8, a demodulator 701 separates information (such as acommunication terminal reception SIR, for example) indicating downlinkchannel quality sent from a communication terminal from a demodulatedreceived signal, and sends this information to a DSCH-using terminaldetermination section 702. In the DSCH-using terminal determinationsection 702, the communication terminal that will use the DSCH isdetermined based on communication terminals that have transmitted arequest signal indicating a wish to use the DSCH, and informationindicating downlink channel quality. That is to say, the DSCH-usingterminal determination section 702 determines terminals to which theDSCH is to be assigned in order of downlink channel quality (high tolow).

[0073] A data selector 704 selects the DSCH data of the communicationterminal that will use the DSCH from the DSCH data of each communicationterminal (MS#1 DSCH data through MS#n DSCH data), adds at the head ofthis selected DSCH data a dummy signal of predetermined length generatedby a dummy signal generator 703, and sends the data to a data modulator110.

[0074] The data modulator 110 performs modulation processing andspreading processing on the DSCH data with a dummy signal added at itshead, and then sends the spread DSCH signal to an AAA directivitycontroller 111. In the AAA directivity controller 111, the DSCH signalfrom the data modulator 110 is multiplied by weights corresponding totransmission directionalities, and the resulting signals are sent to atransmission power controller 705.

[0075] The transmission power controller 705 controls the transmissionpower of the DSCH signals output from the AAA directivity controller111, and then outputs the signals to the communication terminals via thetransmission/reception separator 105 and antennas 101 through 104. Thatis to say, when a dummy signal is transmitted, the transmission powercontroller 705 transmits the dummy signal while gradually increasing thedummy signal transmission power up to a predetermined DSCH signaltransmission power value. Also, when transmission of a dummy signal of apredetermined length ends and DSCH signal transmission is started, thetransmission power controller 705 sets the DSCH signal to thepredetermined transmission power.

[0076] When a dummy signal whose transmission power has been graduallyincreased up to a predetermined DSCH signal transmission power value istransmitted prior to DSCH signal transmission, as described above,interference received from a DSCH signal by a dedicated channel signaltransmitted to a communication terminal located in the vicinity of acommunication terminal to which the DSCH is assigned changes graduallyas shown in FIG. 9.

[0077]FIG. 9 is a drawing showing changes in interference power in acommunication terminal when DSCH assignment is performed by a basestation apparatus according to Embodiment 3 of the present invention.

[0078] That is to say, since a dummy signal whose transmission power hasbeen gradually increased is transmitted prior to the start of DSCHsignal transmission to a communication terminal to which the DSCH isassigned, interference power received from a DSCH signal by acommunication terminal located in the vicinity of a communicationterminal to which the DSCH is assigned changes gradually prior to thestart of DSCH signal transmission, as shown in FIG. 9.

[0079] To be specific, assuming that DSCH signal transmission starts att2 shown in FIG. 9, in the period from t1 to t2 a base station apparatusaccording to this embodiment transmits a dummy signal whose transmissionpower is gradually increased. Thus, in a communication terminal locatedin the vicinity of a communication terminal to which the DSCH isassigned, interference power gradually increases from P0 to P4 in theperiod from t1 to t2 prior to the start of DSCH signal transmission.Consequently, in a communication terminal located in the vicinity of acommunication terminal to which the DSCH is assigned, it is possible fordownlink transmission power control for a dedicated channel signal toadequately track increases in interference power.

[0080] In FIG. 9, P0 indicates interference power received by adedicated channel signal for communication terminal #5 from signalsother than a DSCH signal—that is, interference power received fromdedicated channel signals for other communication terminals within thesame cell, and the like.

[0081] An optimal value is set as appropriate for the rate of increaseof dummy signal transmission power, taking account of the DSCH signaltransmission power and the tracking ability of transmission powercontrol for a downlink dedicated channel signal. It is also possible forthe dummy signal transmission time and transmission power rate ofincrease to be made variable.

[0082] Also, part of the DSCH signal may be transmitted as a dummysignal. That is to say, prior to the start of DSCH signal transmission,the first part of the DSCH signal may be transmitted repeatedly as adummy signal.

[0083] Furthermore, after DSCH signal transmission ends, it is possibleto transmit a dummy signal while gradually decreasing its transmissionpower. By this means, interference power is gradually decreased, andtherefore the tracking ability of transmission power control thatdecreases dedicated channel signal transmission power is improved,enabling system stabilization to be achieved.

[0084] Thus, according to this embodiment, prior to the start of DSCHsignal transmission, a dummy signal is transmitted while graduallyincreasing its transmission power, and consequently interference powerreceived from a DSCH signal increases gradually, and not abruptly, in acommunication terminal located in the vicinity of a communicationterminal to which the DSCH is assigned, so that increases in dedicatedchannel signal transmission power can track increases in interferencepower by means of downlink transmission power control for a dedicatedchannel signal, and deterioration of reception quality due tointerference received from the DSCH signal can be reduced.

[0085] (Embodiment 4)

[0086] In this embodiment, a case is described where the transmissionpower of a dedicated channel signal transmitted to a communicationterminal located in the vicinity of a communication terminal to whichthe DSCH is assigned is increased when DSCH signal transmission isstarted.

[0087]FIG. 10 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 4 of the presentinvention. Parts in FIG. 10 identical to those in Embodiment 1 areassigned the same codes as in Embodiment 1 and their detailedexplanations are omitted.

[0088] In FIG. 10, a demodulator 901 separates information (such as acommunication terminal reception SIR, for example) indicating downlinkchannel quality sent from a communication terminal from a demodulatedreceived signal, and sends this information to a DSCH-using terminaldetermination section 902. In the DSCH-using terminal determinationsection 902, the communication terminal that will use the DSCH isdetermined based on communication terminals that have transmitted arequest signal indicating a wish to use the DSCH, and informationindicating downlink channel quality. That is to say, the DSCH-usingterminal determination section 902 determines terminals to which theDSCH is to be assigned in order of downlink channel quality (high tolow).

[0089] The DSCH-using terminal determination section 902 also specifiesa communication terminal located in the vicinity of a communicationterminal to which the DSCH is assigned from received signal direction ofarrival estimation results output from a direction of arrival estimationsection 106, and notifies a transmission power controller 904 of thespecified communication terminal.

[0090] A dedicated channel data modulator 903 performs modulationprocessing and spreading processing on dedicated channel data for eachcommunication terminal (MS#1 dedicated channel data through MS#ndedicated channel data), and then sends a spread dedicated channelsignal to an AAA directivity controller 111. A dedicated channel datamodulator 903 is provided for each communication terminal (MS).

[0091] When DSCH signal transmission is started, the transmission powercontroller 904 increases the transmission power of a dedicated channelsignal to a communication terminal specified by the DSCH-using terminaldetermination section 902 up to a predetermined value. Also, when DSCHsignal transmission ends and DSCH signal transmission is started, thetransmission power controller 904 decreases the transmission power of adedicated channel signal to a communication terminal specified by theDSCH-using terminal determination section 902 down to the transmissionpower value prior to being increased, restoring it to the originaltransmission power value. Dedicated channel signals whose transmissionpower has been controlled are transmitted to the communication terminalsvia a transmission/reception separator 105, and antennas 101 through104.

[0092] The operation of the transmission power controller 904 isillustrated in FIG. 11. FIG. 11 comprises drawings showing time-wisechanges in dedicated channel signal transmission power and DSCH signaltransmission power in a base station apparatus according to Embodiment 4of the present invention.

[0093] As shown in FIG. 11A and FIG. 11B, in the transmission powercontroller 904, at the same time as DSCH signal transmission tocommunication terminal #1 to which the DSCH is assigned is started attransmission power P, the transmission power of a dedicated channelsignal to communication terminal #2 located in the vicinity ofcommunication terminal #1 is increased by P, equivalent to thetransmission power value of the DSCH signal. That is to say, althoughinterference power received from the DSCH signal to communicationterminal #1 increases, the transmission power of the dedicated channelsignal to communication terminal #2 is increased sufficiently tocompensate for the deterioration of reception quality due to thatincrease in interference power. By this means it is possible fordedicated channel signal reception quality before and after the start ofDSCH signal transmission to be maintained at a predetermined desiredquality in communication terminal #2 located in the vicinity ofcommunication terminal #1 to which a DSCH signal is transmitted.

[0094] In the above description, the amount of increase in the DSCHsignal transmission power value and the amount of increase in thededicated channel signal transmission power value are the same, but theyneed not be the same. That is to say, as the magnitude of interferenceimposed on a dedicated channel signal by a DSCH signal increases as thedistance between the communication terminal to which the DSCH isassigned and a communication terminal located in the vicinity of thatcommunication terminal decreases, it is also possible for an optimalamount of increase in the dedicated channel signal transmission powervalue to be decided upon adaptively according to that distance.

[0095] Thus, according to this embodiment, the transmission power of adedicated channel signal transmitted to a communication terminal locatedin the vicinity of a communication terminal to which the DSCH isassigned is increased when DSCH signal transmission is started, therebymaking it possible for dedicated channel signal reception quality to bemaintained at a predetermined desired quality in a communicationterminal located in the vicinity of a communication terminal to whichthe DSCH is assigned even when DSCH signal transmission is started.

[0096] (Embodiment 5)

[0097] In this embodiment, a case is described where, before DSCH signaltransmission is started, notification of the fact that DSCH signaltransmission is to be started is given to a communication terminallocated in the vicinity of a communication terminal to which the DSCH isassigned, and the communication terminal notified of this requests thebase station to increase transmission power according to the currentdedicated channel signal reception quality.

[0098]FIG. 12 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 5 of the presentinvention. Parts in FIG. 12 identical to those in Embodiment 1 areassigned the same codes as in Embodiment 1 and their detailedexplanations are omitted. FIG. 13 is a main block diagram showing aschematic configuration of a communication terminal apparatus accordingto Embodiment 5 of the present invention.

[0099] In FIG. 12, a demodulator 1101 separates information (such as acommunication terminal reception SIR, for example) indicating downlinkchannel quality sent from a communication terminal from a demodulatedreceived signal, and sends this information to a DSCH-using terminaldetermination section 1102. In the DSCH-using terminal determinationsection 1102, the communication terminal that will use the DSCH isdetermined based on communication terminals that have transmitted arequest signal indicating a wish to use the DSCH, and informationindicating downlink channel quality. That is to say, the DSCH-usingterminal determination section 1102 determines terminals to which theDSCH is to be assigned in order of downlink channel quality (high tolow).

[0100] The DSCH-using terminal determination section 1102 also specifiesa communication terminal located in the vicinity of a communicationterminal to which the DSCH is assigned from received signal direction ofarrival estimation results output from a direction of arrival estimationsection 106, and notifies a notification information creation section1103 of the specified communication terminal. The notificationinformation creation section 1103 creates information (hereinafterreferred to as “transmission start notification information”) fornotifying that DSCH signal transmission has started to the communicationterminal specified by the DSCH-using terminal determination section 1102and a communication terminal located in the vicinity of that specifiedcommunication terminal, and outputs this information to a multiplexer1104 corresponding to the communication terminal specified by thetransmission controller 102. In the multiplexer 1104, the transmissionstart notification information is multiplexed with dedicated channeldata and output to a dedicated channel data modulator 1105.

[0101] The dedicated channel data modulator 1105 performs modulationprocessing and spreading processing on dedicated channel data with whichtransmission start notification information has been multiplexed, andthen sends a spread dedicated channel signal to an AAA directivitycontroller 111. In the AAA directivity controller 111, the dedicatedchannel signal is multiplied by weights corresponding to transmissiondirectionalities, and the resulting signals are sent to a transmissionpower controller 1106 and are transmitted to the communication terminalsvia a transmission/reception separator 105 and antennas 101 through 104.Thus, in the base station, DSCH signal transmission is started to thecommunication terminal to which the DSCH is assigned after transmissionstart notification information transmission has been performed for apredetermined interval.

[0102] Meanwhile, in the communication terminal apparatus shown in FIG.13, a dedicated channel signal with which transmission startnotification information has been multiplexed is received via an antenna102 and transmission/reception separator 1202, and undergoes despreadingprocessing and demodulation processing in a demodulator 1203. By thismeans, dedicated channel data (received data) is obtained.

[0103] Also, a notification information detector 1204 detectstransmission start notification information multiplexed with thedemodulated dedicated channel signal, and outputs a signal indicatingthat this information has been detected to a transmission power controlinformation generator 1205. The transmission power control informationgenerator 1205 generates transmission power control information forperforming dedicated channel signal transmission power control at thebase station, taking the current downlink channel quality intoconsideration, and outputs this information to a multiplexer 1206.

[0104] That is to say, when it is predicted that dedicated channelsignal reception quality will deteriorate due to the start of DSCHsignal transmission and the predetermined desired quality cannot bemaintained, the transmission power control information generator 1205generates transmission power control information directing the basestation to increase the dedicated channel signal transmission powervalue. Also, if dedicated channel signal reception quality is currentlyof excessive quality and it is predicted that dedicated channel signalreception quality can be maintained at the predetermined desired qualityeven if DSCH signal transmission is started, the transmission powercontrol information generator 1205 generates transmission power controlinformation directing the base station to maintain the dedicated channelsignal transmission power value at the current transmission powercontrol. As the DSCH signal transmission power value is known, it ispossible for the transmission power control information generator 1205to estimate approximately to what extent dedicated channel signalreception quality will deteriorate when DSCH signal transmission to acommunication terminal located in the vicinity is started.

[0105] Transmission data (dedicated channel data) with whichtransmission power control information has been multiplexed by themultiplexer 1206 undergoes modulation processing and spreadingprocessing by a modulator 1207, and is then transmitted to the basestation apparatus via the transmission/reception separator 1202 andantenna 1201.

[0106] Then, in the base station apparatus shown in FIG. 12, atransmission power controller 1106 controls dedicated channel signaltransmission power in accordance with the transmission power controlinformation transmitted from the communication terminal. That is to say,when the transmission power controller 1106 predicts that dedicatedchannel signal reception quality cannot be maintained at thepredetermined desired quality due to the start of DSCH signaltransmission, it increases the transmission power of a dedicated channelsignal for a communication terminal located in the vicinity of acommunication terminal to which the DSCH is assigned.

[0107] Thus, according to this embodiment, before DSCH signaltransmission is started, notification of the fact that DSCH signaltransmission is to be started is given to a communication terminallocated in the vicinity of a communication terminal to which the DSCH isassigned, and the communication terminal notified of this requests thebase station to increase transmission power according to the currentdedicated channel signal reception quality, thereby enabling dedicatedchannel signal reception quality to be maintained at a predetermineddesired quality in a communication terminal located in the vicinity of acommunication terminal to which the DSCH is assigned even when DSCHsignal transmission is started.

[0108] In this embodiment, information indicating the difference betweenthe direction of arrival of a signal from the communication terminal towhich the DSCH is assigned and the direction of arrival of a signal froma communication terminal that transmits transmission start notificationinformation may also be included in the transmission start notificationinformation. By this means, a communication terminal notified oftransmission start notification information can perform transmissionpower control that takes this difference in direction of arrival intoconsideration, thereby enabling more accurate transmission power controlto be performed. To be specific, when, for example, the difference indirection of arrival is less than a predetermined threshold value, acommunication terminal notified of transmission start notificationinformation will predict a major effect of increased interference due tothe start of DSCH signal transmission, and will direct the base stationto increase dedicated channel signal transmission power. And if thedifference in direction of arrival is greater than or equal to apredetermined threshold value, a communication terminal notified oftransmission start notification information will predict a minor effectof increased interference due to the start of DSCH signal transmission,and will direct the base station to maintain the dedicated channelsignal transmission power.

[0109] (Embodiment 6)

[0110] In this embodiment, a case is described where a DSCH signal istransmitted with the same directivity to a plurality of communicationterminals for which the received signal direction of arrival is within apredetermined range.

[0111]FIG. 14 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 6 of the presentinvention. Parts in FIG. 14 identical to those in Embodiment 1 areassigned the same codes as in Embodiment 1 and their detailedexplanations are omitted.

[0112] In FIG. 14, a demodulator 1301 separates information (such as acommunication terminal reception SIR, for example) indicating downlinkchannel quality sent from a communication terminal from a demodulatedreceived signal, and sends this information to a DSCH-using terminaldetermination section 1302. In the DSCH-using terminal determinationsection 1302, the communication terminal that will use the DSCH isdetermined based on communication terminals that have transmitted arequest signal indicating a wish to use the DSCH, and informationindicating downlink channel quality. That is to say, the DSCH-usingterminal determination section 1302 determines terminals to which theDSCH is to be assigned in order of downlink channel quality (high tolow).

[0113] The DSCH-using terminal determination section 1302 also divides aplurality of communication terminals that have transmitted a requestsignal indicating a wish to use the DSCH into groups for eachpredetermined direction of arrival range, and controls weights by whicha DSCH signal is to be multiplied by an AAA directivity controller 1303so that a DSCH signal is transmitted with the same directivity tocommunication terminals belonging to the same group.

[0114] That is to say, the DSCH-using terminal determination section1302 takes the communication terminal to which the DSCH is assigned as arepresentative terminal of a group, and takes communication terminalsthat transmit a signal that arrives from a direction within apredetermined range from the direction of arrival of a signaltransmitted from that representative terminal as one group. Then, inorder for a DSCH signal to be transmitted with the same directivity toall communication terminals belonging to the same group, the DSCH-usingterminal determination section 1302 outputs information indicating thedirection of arrival of a signal transmitted from the representativeterminal of a group (that is, information indicating the direction ofthe representative terminal of a group from among direction of arrivalinformation estimated by a direction of arrival estimation section 106)to an AAA directivity controller 1303 corresponding to communicationterminals belonging to that group.

[0115] The AAA directivity controller 1303 forms a transmissiondirectivity based on information indicating direction of arrival outputfrom the DSCH-using terminal determination section 1302. That is to say,the AAA directivity controller 1303 multiplies all DSCH signals tocommunication terminals belonging to the same group by the same weight.DSCH signals multiplied by a weight are transmitted to the respectivecommunication terminals from antennas 101 through 104 via atransmission/reception separator 105.

[0116] Next, DSCH signal transmission directivity control according tothis embodiment will be described in detail. FIG. 15 is a drawingshowing radiation patterns for explaining transmission directivitycontrol performed by a base station apparatus according to Embodiment 6of the present invention.

[0117] In FIG. 15, it is assumed that request signals indicating a wishto use the DSCH are transmitted by communication terminals #1 through#7. Reference code 201 indicates the nondirectional transmission area.

[0118] The DSCH-using terminal determination section 1302 firstdetermines the DSCH assignment order according to downlink channelquality. Here, downlink channel quality is assumed to improve in orderfrom communication terminal #1 through communication terminal #7. Thus,the DSCH assignment order determined by the DSCH-using terminaldetermination section 402 is communication terminal #1 throughcommunication terminal #7.

[0119] Next, the DSCH-using terminal determination section 1302 takescommunication terminal #1 to which the DSCH is first assigned as a grouprepresentative terminal, and, based on direction of arrival estimationresults, detects terminals transmitting a signal that arrives from adirection within a predetermined range of angles with reference to thedirection of arrival of a signal transmitted from communication terminal#1. Here, it is assumed that the only communication terminaltransmitting a signal that arrives from a direction within thepredetermined range of angles from the direction of arrival of a signaltransmitted from communication terminal #1 is communication terminal #2.

[0120] The DSCH-using terminal determination section 1302 then outputsinformation indicating the direction of arrival of a signal transmittedfrom communication terminal #1 to both the AAA directivity controller1303 for communication terminal #1 and the AAA directivity controller1303 for communication terminal #2. By this means, the DSCH signal forcommunication terminal #1 and the DSCH signal for communication terminal#2 are multiplied by the same weight in accordance with the direction ofarrival of the signal transmitted from communication terminal #1, andare transmitted after the same transmission directivity 1401 has beenformed for them.

[0121] Next, the DSCH-using terminal determination section 1302 takescommunication terminal #3 to which the DSCH is next assigned as a grouprepresentative terminal, and controls a weight for multiplication by theAAA directivity controller 111 in the same way as for communicationterminal #1 and communication terminal #2. Thus, the DSCH signal forcommunication terminal #3 and the DSCH signal for communication terminal#4 are transmitted after the same transmission directivity 1402 has beenformed for them.

[0122] Thereafter, similar operations are performed, and the DSCH signalfor communication terminal #5, the DSCH signal for communicationterminal #6, and the DSCH signal for communication terminal #7 aretransmitted after the same transmission directivity 1403 has been formedfor them.

[0123] The size of the predetermined range of angles with reference to asignal transmitted from a representative terminal is set taking thebalance between the number of times transmission directivity is switchedand the decrease in interference due to transmission directivityformation into consideration.

[0124] Thus, according to this embodiment, communication terminals towhich the DSCH is to be assigned are divided into a number of groups,and a DSCH signal is transmitted with the same directivity formed to allcommunication terminals belonging to the same group, thereby enablingthe number of times DSCH signal transmission directivity is switched tobe reduced. By this means, the greater the number of communicationterminals belonging to the same group, the greater is the reduction inthe frequency with which interference power received from a DSCH signalchanges suddenly in a communication terminal located in the vicinity ofa communication terminal to which the DSCH is assigned, and the longeris the interval during which interference power is held constant. Thus,in a communication terminal located in the vicinity of a communicationterminal to which the DSCH is assigned, it becomes possible forincreases in dedicated channel signal transmission power to trackchanges in interference power by means of downlink transmission powercontrol for a dedicated channel signal, and it is possible to reducedeterioration of reception quality due to interference received from aDSCH signal.

[0125] In above Embodiments 1 through 6, descriptions have been giventaking the example of a radio communication system in which downlinkhigh-speed data communication is performed using a DSCH, but this is nota limitation, and the present invention can also be applied to any radiocommunication system in which a base station performs downlinkhigh-speed data communication by determining shared channel assignmentin accordance with information transmitted from communication terminals.

[0126] As described above, according to the present invention it ispossible to prevent a major deterioration of dedicated channel signalreception quality even when an adaptive array is used for shared channelsignal transmission, thereby enabling good downlink communicationconditions to be maintained.

[0127] This application is based on Japanese Patent Application No.2000-197132 filed on Jun. 29, 2000, entire content of which is expresslyincorporated by reference herein.

[0128] Industrial Applicability

[0129] The present invention is applicable to any radio communicationsystem in which a base station performs downlink high-speed datacommunication by determining shared channel assignment in accordancewith information transmitted from communication terminals.

1. A base station apparatus comprising: an estimator that estimates adirection of arrival of a signal transmitted from each communicationterminal apparatus; a determiner that determines an assignment order ofa shared channel that is shared by a plurality of communication terminalapparatuses and assigned on a per predetermined transmission unit basis,in association with the direction of arrival; and a transmitter thatforms a directivity for the direction of arrival and transmits a sharedchannel signal to said each communication terminal apparatus inaccordance with the order.
 2. The base station apparatus according toclaim 1, wherein said determiner determines a communication terminalapparatus that transmits a signal that arrives from a direction forwhich a difference from a direction of arrival of a signal transmittedfrom a communication terminal apparatus to which the shared channel isassigned this time is smallest as a communication terminal apparatus towhich the shared channel will be assigned next time.
 3. A base stationapparatus comprising: an estimator that estimates a direction of arrivalof a signal transmitted from each communication terminal apparatus; adeterminer that determines an assignment order of a shared channel thatis shared by a plurality of communication terminal apparatuses andassigned on a per predetermined transmission unit basis, according to avalue calculated from a priority assigned in association with downlinkchannel quality and a value indicating the direction of arrival; and atransmitter that forms a directivity for the direction of arrival andtransmits a shared channel signal to said each communication terminalapparatus in accordance with the order.
 4. A base station apparatuscomprising: an estimator that estimates a direction of arrival of asignal transmitted from each communication terminal apparatus; adeterminer that determines an assignment order of a shared channel thatis shared by a plurality of communication terminal apparatuses andassigned on a per predetermined transmission unit basis, in associationwith downlink channel quality; and a transmitter that forms adirectivity for the direction of arrival and, prior to a start oftransmission of a shared channel signal transmitted to said eachcommunication terminal apparatus in accordance with the order, transmitsa dummy signal whose transmission power is increased gradually up to apredetermined transmission power value of the shared channel signal. 5.A base station apparatus comprising: an estimator that estimates adirection of arrival of a signal transmitted from each communicationterminal apparatus; a determiner that determines an assignment order ofa shared channel that is shared by a plurality of communication terminalapparatuses and assigned on a per predetermined transmission unit basis,in association with downlink channel quality; a transmitter that forms adirectivity for the direction of arrival and transmits a shared channelsignal to said each communication terminal apparatus in accordance withthe order; and a transmission power controller that increasestransmission power of a dedicated channel signal transmitted to acommunication terminal apparatus that exists in the vicinity of acommunication terminal apparatus to which the shared channel signal istransmitted by a predetermined amount during transmission of the sharedchannel signal.
 6. A base station apparatus comprising: an estimatorthat estimates a direction of arrival of a signal transmitted from eachcommunication terminal apparatus; a determiner that determines anassignment order of a shared channel that is shared by a plurality ofcommunication terminal apparatuses and assigned on a per predeterminedtransmission unit basis, in association with downlink channel quality; atransmitter that forms a directivity for the direction of arrival andtransmits a shared channel signal to said each communication terminalapparatus in accordance with the order; a notifier that, prior to astart of transmission of the shared channel signal, notifies acommunication terminal that exists in the vicinity of a communicationterminal apparatus to which the shared channel signal is transmitted ofthe fact that transmission of the shared channel signal is to start; anda transmission power controller that increases transmission power of adedicated channel signal to said communication terminal apparatus thatexists in the vicinity in accordance with a request from saidcommunication terminal apparatus that exists in the vicinity.
 7. Acommunication terminal apparatus that performs radio communication withthe base station apparatus according to claim 6, said communicationterminal apparatus comprising: a detector that detects that the factthat the shared channel signal transmission is to start has beennotified from said base station apparatus; and a transmitter that, whenit is determined that reception quality of the dedicated channel signalwill deteriorate beyond a predetermined desired quality due to a startof transmission of the shared channel signal, transmits to said basestation apparatus a request signal requesting that transmission power ofthe dedicated channel signal be increased.
 8. A base station apparatuscomprising: an estimator that estimates a direction of arrival of asignal transmitted from each communication terminal apparatus; adeterminer that determines an assignment order of a shared channel thatis shared by a plurality of communication terminal apparatuses andassigned on a per predetermined transmission unit basis, in associationwith downlink channel quality, and also sets a group that includes atleast one communication terminal apparatus in association with thedirection of arrival; and a transmitter that forms a directivity foreach the group, and using the directivity transmits a shared channelsignal in accordance with the order to all communication terminalapparatuses included in the group.
 9. A radio communication methodcomprising: an estimating step of estimating a direction of arrival of asignal transmitted from each communication terminal apparatus; adetermining step of determining an assignment order of a shared channelthat is shared by a plurality of communication terminal apparatuses andassigned on a per predetermined transmission unit basis, in associationwith the direction of arrival; and a transmitting step of forming adirectivity for the direction of arrival and transmitting a sharedchannel signal to said each communication terminal apparatus inaccordance with the order.
 10. The radio communication method accordingto claim 9, wherein said determining step determines a communicationterminal apparatus that transmits a signal that arrives from a directionfor which a difference from a direction of arrival of a signaltransmitted from a communication terminal apparatus to which the sharedchannel is assigned this time is smallest as a communication terminalapparatus to which the shared channel will be assigned next time.
 11. Aradio communication method comprising: an estimating step of estimatinga direction of arrival of a signal transmitted from each communicationterminal apparatus; a determining step of determining an assignmentorder of a shared channel that is shared by a plurality of communicationterminal apparatuses and assigned on a per predetermined transmissionunit basis, according to a value calculated from a priority assigned inassociation with downlink channel quality and a value indicating thedirection of arrival; and a transmitting step of forming a directivityfor the direction of arrival and transmitting a shared channel signal tosaid each communication terminal apparatus in accordance with the order.12. A radio communication method comprising: an estimating step ofestimating a direction of arrival of a signal transmitted from eachcommunication terminal apparatus; a determining step of determining anassignment order of a shared channel that is shared by a plurality ofcommunication terminal apparatuses and assigned on a per predeterminedtransmission unit basis, in association with downlink channel quality;and a transmitting step of forming a directivity for the direction ofarrival and, prior to a start of transmission of a shared channel signaltransmitted to said each communication terminal apparatus in accordancewith the order, transmitting a dummy signal whose transmission power isincreased gradually up to a predetermined transmission power value ofthe shared channel signal.
 13. A radio communication method comprising:an estimating step of estimating a direction of arrival of a signaltransmitted from each communication terminal apparatus; a determiningstep of determining an assignment order of a shared channel that isshared by a plurality of communication terminal apparatuses and assignedon a per predetermined transmission unit basis, in association withdownlink channel quality; a transmitting step of forming a directivityfor the direction of arrival and transmitting a shared channel signal tosaid each communication terminal apparatus in accordance with the order;and a transmission power controlling step of increasing transmissionpower of a dedicated channel signal transmitted to a communicationterminal apparatus that exists in the vicinity of a communicationterminal apparatus to which the shared channel signal is transmitted bya predetermined amount during transmission of the shared channel signal.14. A radio communication method comprising: an estimating step ofestimating a direction of arrival of a signal transmitted from eachcommunication terminal apparatus; a determining step of determining anassignment order of a shared channel that is shared by a plurality ofcommunication terminal apparatuses and assigned on a per predeterminedtransmission unit basis, in association with downlink channel quality; atransmitting step of forming a directivity for the direction of arrivaland transmitting a shared channel signal to said each communicationterminal apparatus in accordance with the order; a notifying step of,prior to a start of transmission of the shared channel signal, notifyinga communication terminal that exists in the vicinity of a communicationterminal apparatus to which the shared channel signal is transmitted ofthe fact that transmission of the shared channel signal is to start; anda transmission power controlling step of increasing transmission powerof a dedicated channel signal to said communication terminal apparatusthat exists in the vicinity in accordance with a request from saidcommunication terminal apparatus that exists in the vicinity.
 15. Theradio communication method according to claim 14, further comprising: adetecting step of detecting that the fact that the shared channel signaltransmission is to start has been notified from said base stationapparatus; and a transmitting step of, when it is determined thatreception quality of the dedicated channel signal will deterioratebeyond a predetermined desired quality due to a start of transmission ofthe shared channel signal, transmitting to said base station apparatus arequest signal requesting that transmission power of the dedicatedchannel signal be increased.
 16. A radio communication methodcomprising: an estimating step of estimating a direction of arrival of asignal transmitted from each communication terminal apparatus; adetermining step of determining an assignment order of a shared channelthat is shared by a plurality of communication terminal apparatuses andassigned on a per predetermined transmission unit basis, in associationwith downlink channel quality, and also setting a group that includes atleast one communication terminal apparatus in association with thedirection of arrival; and a transmitting step of forming a directivityfor each the group, and, using the directivity, transmitting a sharedchannel signal in accordance with the order to all communicationterminal apparatuses included in the group.